Birthplace is consistently given as California, although biography states he was born in Utah and the family moved to California when he was an infant. I am using California as birthplace because it is supported by documentation. He may have been a twin of Agnes.
.1860 census: living with parents and siblings in Pajaro, CA
1870 census: living with father and siblings in Pajaro, Santa Cruz Co, CA. Attending school.
1880 census: living with brother's family in Gilroy, CA.

1910 census: may be John R. Adam, single, living in San Antonio, Monterey Co, CA. Farmer. Born California, both parents born in Scotland. Age 54.

Death date source is California death index, 1905-1939 on ancestry.com

The following biography was posted on Ancestry.com by widget3523:
Jim was the second son of William Thom and Margaret (Thomson) Adam. William Thom Adam was born 7 May 1793 and died 5 Jan 1875. Jim's mother, Margaret was born in 1821 and died abt. 1900.
Jim was born in Salt Lake City, Utah and was an infant when the family moved to California.
Jim never married. He lived for a long time with his mother after his father died, near Jolon, Monterey Co., Ca. His mother is quoted as saying that she got 'real tired of cooking for him'. Eventually, he moved in with his half-brother and nephew, Alexander and Bill.
James was the first Postmaster in the first Post Office of the Gem area. His nephew, William Zimry 'Bill' Adam, carried the mail by horse and cart in 1913. When the creeks were up because of the rain, he went by horseback, thereby still managing to ford them and get the mail through. At a future time, 1923, the mail was also carried by Bill's son-in-law, Clyde Dayton, who took it to Pleyto, Bryson and Bradley, all of which are in Monterey Co., Ca.
Jim died in 1923.
Source of above information: Lusana Hubbard